Wetbench SOP

Nanofabrication Facility: Wetbench SOP Rev. 03, 01/13

Author: Mario Beaudoin, Email: beaudoin@physics.ubc.ca, Phone: 604-822-1853.

wetbench

Purpose
To standardize operating procedures for the lithography room wetbenches and spinners in order to ensure operator safety and process cleanliness. This SOP is not meant to replace the AMPEL Nanofabrication Facility Members’ Laboratory Guide which can be found on the webpage. Please read the Laboratory Guide carefully.

Hours of operation and buddy system

  • Regular hours are from 9:00 am to 6:00 pm on normal weekdays
  • The buddy system is in force at all times for “dangerous” processes
  • A remote buddy system is in force for “relatively safe” processes as described below. (A remote buddy is someone with FULL access to AMPEL, is in the building and only a phone call away and will check on you at specific intervals)

Qualification Levels

  • Basic: users can use the spinners, DI water, acetone, methanol, ipa, resists, and developer. These, and only these, processes are also permitted after hours with a “remote buddy”.
  • Strong acids: users need to verify their process with the cleanroom manager and get independent qualification on both usage and disposal.
  • HF and BOE: this is potentially our most dangerous chemicals and require an independent qualification.

Safety
Every user should know and be able to answer questions on:

  • How to handle chemicals
  • Where to find the protective gear
  • how to dispose of aqueous chemicals
  • how to dispose of organic chemicals properly
  • where MSDS’s are
  • how to determine the chemical compatibility of a glove
  • what to do in case of a chemical spill (small, large)
  • what to do in case of an HF spill
  • what to do in case of HF exposure
  • how to store chemicals properly

Process Cleanliness
Every user should know and be able to answer questions on:

  • principle of the wetbench operation
  • materials incompatible with the wetbench
  • how to pour aqueous chemicals out of bottles

The Wetbenches
The cleanroom wetbenches consist of a laminar flow with a net inward air flow. The wetbench on the left side as you enter the yellow room is the “new” wetbench whereas the one on the right is the “old” wetbench. The air is blown from the top and exhausted at the bottom through the vent grids. For this flow to function optimally, it is important that the vent grids not be blocked. A common mistake is to place paper wipes on the front exhaust grids. It is important to make sure that the wetbench fan is turned on so that the laminar flow is operational. There is a big red button on the front center of the old wetbench which turns off the power to the outlets also found on the front (see Figure 1). The new wetbench does not have this red button. The wetbenches contain some common use items: tweezers (metal and fluoroware), timers, thermometers, development trays (5×7 in photographic trays), squeeze bottles (acetone, propanol, methanol). There is also a glassware drying rack and a limited amount of common use glassware (beakers, graduated cylinders, etc.). In addition, there are digital hotplates, ultra-sonic (US) baths and spinners. You will also find two clearly identified waste solvent beakers which are to be used for temporary recuperation of solvents (eg when using the squeeze bottles). One beaker, labelled “non-halo” is used to recuperate non halogenated solvents. The other beaker, labelled “halo”, is used for halogenated solvents. Halogenated solvents are those containing halogens (next to last column of the periodic table F, Cl, Br, I & At). In the cleanroom, we mostly only have chlorinated solvents such as chlorobenzene and trichloroethylene. On either end of the old wetbench are sinks with a DI water gooseneck, a DI water gun and a nitrogen gas gun. The goosenecks and guns have taps in the front of the wetbench. In the middle of the wetbench is a small double-sink originally designed for rinsing; we are not currently using it. The new wetbench has a single sink but 2 DI water guns. It also has a tap water gooseneck on its north end; this is usually connected to the TMAH silicon etching setup.

Wetbench Chemicals

The Nanofabrication Facility keeps an inventory of commonly used chemicals which are stored under the wetbenches and in the flammables cabinet. Note that chemicals under the wetbench are separated according to compatibility in properly labelled secondary containers. These include CMOS or electronic grade acids and solvents, as well as some photoresist, developer and stripper. If you bring in a new container from the stock area, be sure to wipe the outside of the container in the gowning area before bringing it in the cleanroom proper. Chemicals belonging to a research group (hence, not common use) should be clearly identified with the owner’s name. Etiquette calls for not using these unless you have spoken with a member of that group first. Unless your process calls for abnormally large quantities of chemicals, you are welcomed to use any clearly identified cleanroom chemical. If you want to introduce a new chemical in the cleanroom, please discuss with the cleanroom manager beforehand to ensure compatibility with current process.
Pouring of chemicals from bottles or containers (dry chemicals) is the most common source of contamination. Avoid touching the lip of chemical bottles to any glassware or other recipient while pouring. To ensure your own safety, you top hand should hold the bottle handle while your bottom hand is holding the bottle bottom from the same side as the handle (avoids dripping chemicals from reaching your hands). After pouring acid from a bottle, put the lid back on, put the bottle in one of the sinks and rinse the outside with the DI water gun. Wipe the outside of the bottle with a wipe and store the bottle back in its proper area. Photoresist is normally poured from the larger bottle into smaller brown glass bottles and left to settle. Best practice supposes that clean single use pipettes are then used to aspire photoresist out of the bottle and dropped directly onto your sample in the spinner; this avoids stirring up the particulate deposits in the bottom of the photoresist bottle. All flammable chemicals (eg solvents, photoresist) are stored in the flammables cabinets next to the old wetbench.

Wetbench Shared Glassware
We recommend that users bring their own glassware. A limited number of such items are supplied as shareware, which can be useful for infrequent users, but experience has shown that one cannot trust the cleanliness of shared glassware. The glassware is found in a tupperware box kept on top of the drybench; glassware should be returned in that box after it has dried. These beakers have been cleaned and are labelled for the chemical that can be used in them. Only use chemicals in beakers specifically identified for that chemical. Beakers and other glassware are never wiped: this actually contaminates them. Beakers used for solvents may be rinsed with acetone, propanol and DI water and are then hanged to dry. Beakers used for acids are thoroughly rinsed with DI water before being hanged to dry.

Safety:

The MSDS sheets
MSDS sheets can be found through the UBC safety website (http://riskmanagement.ubc.ca/); specifically at http://riskmanagement.ubc.ca/health-safety/chemical-safety/materials-saf…. The computer next to the microscope should have a bookmark to it; if not, start from http://riskmanagement.ubc.ca/ and navigate.
The buddy system
Always remember that, in principle, no one should work alone in the lab for obvious safety reasons. Since the AMPEL cleanroom is so small however, we are allowing a remote buddy system for “safe” processes (spinners, DI water, acetone, methanol, ipa, resists, and developer). A remote buddy is one that is immediately available by phone, is in AMPEL and has key access to all important parts of the building, can come to your assistance within minutes and will periodically check up on you either by phone or in person.
Protective equipment
Always wear the safety glasses when working in the yellow room if anyone in there is working with chemicals. Wear the splash goggles when handling chemicals at the wetbench. For more protection, such as when handling HF, wear the full faceshield and the green aprons. Please report inadequate equipment to the cleanroom manager; the face shields should allow sufficient vision and the aprons should not be torn to bits. Gloves are also an important concern when handling chemicals. The laboratory supplies latex (rubber), nitrile and the thick “acid” gloves. The specifications and protective ratings of each glove type is posted on the side of the shelves in the gowning area. Always choose a glove that’s appropriate for the chemical you are working with.
As you walk through the lab, please pay particular attention to the locations of the safety shower, eyewash station, first aid kit, fire extinguisher, and emergency exits. These are indicated in the Laboratory Guide.
Water is your friend
Always work safely but be aware that the risk of splashing chemicals on yourself is never nil. Should you spill a small amount of chemicals on yourself, you should always have an immediate access to flowing water. Turn on the goose neck DI before manipulating chemicals and leave it running while you are working. The DI water gun is your next line of defense. Do not hesitate to use it to rinse off chemicals that may have spilled on yourself or the wetbench. Remember that safety, yours and others’, comes first before any other consideration. There is an eyewash station and a safety shower in the gowning area. If you splash anything in your eyes however, the DI water gun is probably faster. If you spill some HF on yourself, rinse the area with large amounts of water, then use the ointment in the tube on the wetbench (see Figure 1).
Reporting Accidents
The hospital is a short walk from AMPEL. It is better to overreact and have peace of mind. If in any doubt about your exposure level, please consult a physician. Please also report all accidents to your advisor and the cleanroom manager.

Chemical Waste Disposal

Empty Chemical Bottles
When you have emptied a chemical bottle, plastic or glass, rinse it thoroughly 3 times. While rinsing bottles that contained acids or chlorinated solvents, wear a face shield and chemical resistant gloves. Once it has been rinsed 3 times, the bottle can be taken out of the lab. Clean bottles can be left next to the metal bench in the gowning area.
Mixing Chemicals Can Be Dangerous!
It is imperative that chemicals be discarded properly (see table below). Mixing chemicals carelessly can be extremely dangerous. Acids, bases and solvents should never be mixed together in the same container as this is a potentially explosive reaction.
There are labeled red disposal cans in the flammables cabinets for non-halogenated organic solvents and halogenated (chlorinated) organic solvents. It is important to dispose of waste chemicals in their proper waste containers.
HF and BOE (buffered oxide etch; contains 5-10% HF) should never be dumped in the sink: there is a special waste HF & BOE bottle in the old wetbench.
Small quantities (100ml or less) of acids or bases may be dumped it in the sink and washed with large quantities of DI water; make sure that the entire sink, sides and bottom, is thoroughly rinsed with DI water afterwards (use the water gun). For larger quantities, use a large beaker of water and dump your acid waste in it. Then, dump this large beaker in the sink and proceed as for small quantities. AMPEL has acid drains so it is safe to dispose of your acids this way.
Recycling solvents
As much as possible, we recommend that all solvents be collected; for solvents used with the squeeze bottles, a large waste solvent beaker is provided in the wetbench. This large beaker is then emptied into the proper red cans at the end of the session.
Undiluted, non-water-miscible and chlorinated solvents, such as TCA, photoresist or chlorobenzene should NEVER be dumped in the sink. Disposal of solvents in this manner is not only an environmental threat, it will also damage the building’s plumbing. Chlorobenzene can in fact be saved in a clean and IDENTIFIED capped bottle for personal reuse.
Photoresist that is significantly diluted with acetone can be poured into the plastic organic waste red cans in the flammables cabinets.
Other chemicals
If you need to dispose of a chemical which does not fall under the preceding categories and for which no waste container already exists, the waste should be placed in a loosely capped plastic bottle with a label clearly identifying the contents. The bottle should be placed underneath the wetbench (or with the flammables if flammable) but care should be exercised to ensure that incompatible chemicals are not stored next to each other.
You must clearly identify the waste bottle with:

  1. your name
  2. the material identification (ie chemical common name – eg sulfuric acid not H2SO4)
  3. descriptive information such as corrosive/poison/explosive etc.
You must also notify the cleanroom manager. If the waste containers are full, notify the cleanroom manager or a lab assistant.
Wipes
Wipes that have been soaked with acids or bases should be thoroughly rinsed in the sink before being disposed of in the garbage can inside the lithography room.
Wipes that have been soaked with solvents should be left to dry under the laminar flow hood (wetbench) in the properly identified plastic container. Once the
solvents have evaporated, they may be put in ziplock bags and thrown in the garbage.

Transporting Chemicals Safely
When bringing chemicals into the lab, you must use the safety bottle carriers provided in the gowning or monitoring areas. When you are finished with the carriers, PLEASE return them to this area so that they will be available for others to use. Also, be sure to check your immediate work area and the yellow room for open bottles of the desired chemical before bringing a new bottle into the lab.

Telephones
The lab has one new VOIP telephone set located in the lithography (yellow) room. Please refer to the Laboratory Guide for telephone etiquette. In an emergency, 911 works. To dial help from someone on campus, dial 2- (or 7-) and the last 4 numbers of the telephone number. To dial outside campus, dial 9 before dialing the entire telephone number.

Chemical Spills
All spills, whether at a sink or work surface, must be cleaned up at once, when you are 100% certain that it is safe to do so. Leave work areas as you would like to find them. Reminder: water and acid/HF look the same. The best way to clean the wetbench is to use the DI water gun. If using wipes, for instance to clean a few drops from the floor, follow the instruction for their disposal. If an accidental large spill occurs and you are concerned about safety, evacuate the room (press the big red button next to the exit door to sound the alarm), make sure everyone else also evacuates, secure the area and use the telephone in another room to report the spill and consult for a plan of action. Reminder: large quantities of solvent fumes (acetone, propanol, methanol or even ethanol) can be fatal with less warning signs than acids. Always know the telephone number where you can reach someone (buddy system). Don’t be afraid to over-react to a chemical accident or spill: better to look stupid, and be unharmed, than to brashly act stupid and live with consequences.

Cleanliness
The cooperation of all students and users is required to keep the wetbenches and spinners clean. It is expected, as a matter of cleanroom etiquette, that users wipe down the wetbench after each use. If you must leave samples or labware in the wetbench for some time, make sure to identify it clearly, including where you may be reached and when you will be returning. Try to return as soon as possible (normally within an hour or two).

Equipment Reservations
All equipment reservation is done online using the BUMBLEBEE reservation system.

Work Storage

  • Ask the cleanroom manager for shelf space in the rooms you use most often. Alternatively, you may store labeled closed boxes in the shelves on the “dirty” side in the gowning room (remember to wipe them down with iso-propanol when taking them back in the clean areas). Always store your parts after you have completed your
    work for the day.
  • The cleanroom has limited space for lab member storage. Members are asked to expediently clean out shelves and then remove their nametags and marker tape when they are no longer needed. Send e-mail to beaudoin@physics.ubc.ca so these spaces can be reassigned. Space that has not been used in a long time will be reassigned to more regular users.

Chemical Disposal Summary

HF, BOE (contains HF)
Pour in the HF waste bottle; Put bottle in sink, pour into bottle using a funnel, cap the bottle and rinse the funnel, the bottle, the sink and your beakers with copious amounts of water. Wipe outside of bottle and put back in its place. The waste HF bottle is stored with the other HF compatible acids in the storage space under the old wetbench.
Other acids or acid solutions compatible with water.
For less than 100 ml; pour in the sink under running water. Rinse your beakers and the sink thoroughly with water. For more than 100 ml, take a large beaker half full with water and slowly pour your acid solution into it. Dispose of water+acid solution as you do with 100 ml quantities. Repeat as necessary.
Bases (also most developpers if not overly contaminated by photoresist)
Follow the same procedure as with acids.
Developer with visible photoresist contamination
Disposed in the appropriate waste developer bottle if available. If not, create a waste developer bottle making sure it is clearly labeled.
HMDS (photoresist primer)
There is a waste container in the flammables cabinet. HMDS should never be mixed with water or alcohol.
Non-Halogenated organic solvents (egIPA, Acetone, Methanol)
Use the specifically marked beaker (Non-Halo) on the wetbench for temporary disposal. Remember to empty the beaker in the nonhalogenated
waste (read tag) red can found in the flammables cabinet.
Halogenated organic solvents (eg chlorobenzene, trichloroethylene)
Use the specifically marked beaker (Halo) on the wetbench for temporary disposal. Remember to empty the beaker in the halogenated waste (read tag) red can found in the flammables cabinet. Some users actually reuse chlorobenzene which is fine.
Photoresist
Dilute with acetone and dispose of as with other non-halogenated solvents.
Other liquids or substances?
Bring the MSDS sheets with you and discuss with the cleanroom manager to determine a safe way of storing and disposing. NB: no
inherently unsafe substance will be allowed in the cleanroom.